This printing unit consists of an inking module and a blanket cylinder, which are independent of one another, in such a manner as to enable the inking module to be used alone or conjointly with the blanket cylinder.
In one form the invention is defined in that the numbering device with which the press is equipped is replaced by the blanket cylinder of the printing unit working with the inking module, and use is made of the drive mechanism and pressure adjustment mechanism provided in the press to obtain for each printing cycle, instead of the numbering, an additional color obtained by color superimposition.
In the other form of the invention the same inking module, disposed in another position in the press, works conjointly with the blanket cylinder of the press to enable for each printing cycle an additional color and optionally numbering to be achieved.